Objective:

This study aimed to investigate the ocular motor abnormalities with their anatomical correlation in dorsolateral pontine (DLP) lesions.

Background:

Dorsolateral portion of the caudal pons contains the vestibular nucleus and inferior cerebellar peduncle (ICP) that play important roles in conveying and processing vestibular and ocular motor signals. The aim of this study was to investigate abnormal ocular motor findings in DLP lesions to help differentiate them from AVS resulting from benign peripheral vestibulopathy, and determine their anatomical correlation.

Design/Methods:

Of the 506 patients with pontine infarction in the stroke registry, 18 patients with unilateral DLP lesions (17 with cerebral infarction and one with cavernous malformation) were subjected to analyses of clinical features, and results of neuro-otological evaluations and neuroimaging. 

Results:

Most patients (n=16) presented with an isolated acute vestibular syndrome (AVS). The involved structures within the DLP were ICP in four and vestibular nucleus in the remaining 14. The unilateral ICP lesion showed consistent abnormalities in vestibular and ocular motor tests including ipsilesional nystagmus without gaze-evoked nystagmus (GEN), normal head impulse tests (HITs) and caloric response. Whereas, lesions of the vestibular nucleus showed a broader range of eye movement abnormalities including ipsi-or contralesional nystagmus with GEN, positive HITs, normal or abnormal caloric responses, or fixation nystagmus. Initial MRIs with diffusion-weighted images (< 48 hours) were falsely negative in 41% (n=7) of DLP infarction. 

Conclusions:

This study demonstrates that unilateral DLP lesions frequently present isolated AVS with diverse ocular motor abnormalities. These characteristics may be due to complex involvements of afferent or efferent fibers to and from vestibular nucleus.